CN116778973A

CN116778973A - Magnetic disk device and servo pattern writing method

Info

Publication number: CN116778973A
Application number: CN202210578272.4A
Authority: CN
Inventors: 松永俊孝
Original assignee: Toshiba Corp; Toshiba Electronic Devices and Storage Corp
Current assignee: Toshiba Corp; Toshiba Electronic Devices and Storage Corp
Priority date: 2022-03-09
Filing date: 2022-05-25
Publication date: 2023-09-19
Also published as: US20230290374A1; US11869554B2; JP2023131391A

Abstract

Provided is a magnetic disk device capable of improving reliability and a servo pattern writing method. The magnetic disk device according to the present embodiment includes: a disk; a head that writes data to the disk and reads data from the disk; and a controller that writes a 2 nd spiral servo pattern different from the 1 st spiral servo pattern so as to overlap the 1 st spiral servo pattern with a shift in a radial direction of the disk.

Description

Magnetic disk device and servo pattern writing method

The present application enjoys priority of Japanese patent application No. 2022-036125 (application date: day 3, month 9 of 2022). The present application includes the entire contents of the basic application by reference to the basic application.

Technical Field

Embodiments of the present application relate to a magnetic disk apparatus and a servo pattern writing (Servo Pattern Write) method.

Background

In a blank disk writing (BDW: blank Disc Writing) step of writing a spiral servo pattern (Spiral Servo Pattern), a magnetic disk device writes a plurality of spiral servo patterns on a disk having no data or patterns written therein by a Head (Head). In a Self-Servo writing (SSW) process, a magnetic disk apparatus writes a plurality of Servo patterns (hereinafter, also referred to as product Servo patterns) used in a final product by a head based on a plurality of spiral Servo patterns.

In the magnetic disk apparatus, when the write width of the head is narrow, the width of the spiral servo pattern is narrowed, and thus the number of synchronization marks (sync marks) included in the read signal for detecting the spiral servo pattern is reduced. In addition, in the magnetic disk apparatus, the number of sync marks detected by reading the spiral servo pattern by the head in seek (seek) is smaller than the number of sync marks detected by reading the spiral servo pattern by the head in track (on track), and therefore there is a possibility that no sync mark is detected in seek and servo is disengaged. For this reason, the reliability of the process of SSW may be lowered.

Disclosure of Invention

The embodiment of the invention aims to provide a magnetic disk device and a servo pattern writing method capable of improving reliability.

The magnetic disk device according to the present embodiment includes: a disk; a head that writes data to the disk and reads data from the disk; and a controller that writes a 2 nd spiral servo pattern different from the 1 st spiral servo pattern so as to overlap the 1 st spiral servo pattern with a shift in a radial direction of the disk.

Drawings

Fig. 1 is a block diagram showing the structure of a magnetic disk device according to embodiment 1.

Fig. 2 is a schematic diagram showing an example of the arrangement of the head with respect to the disk according to embodiment 1.

Fig. 3 is a schematic diagram showing an example of a write (write) signal of a spiral servo pattern.

Fig. 4 is a schematic diagram showing an example of a write (writing) processing method of a normal spiral servo pattern.

Fig. 5 is a schematic diagram showing an example of a write processing method of a normal spiral servo pattern.

Fig. 6 is a schematic diagram showing an example of a write processing method of the superimposed write spiral servo pattern according to the present embodiment.

Fig. 7 is a schematic diagram showing an example of a table of offset (offset) amounts of the superimposed spiral servo patterns according to the present embodiment.

Fig. 8 is a schematic diagram showing an example of a write processing method of the superimposed write spiral servo pattern according to the present embodiment.

Fig. 9 is a schematic diagram showing an example of a write processing method of the superimposed write spiral servo pattern according to the present embodiment.

Fig. 10 is a schematic diagram showing an example of a method for calculating the spiral pattern center position of a normal spiral servo pattern.

Fig. 11 is a schematic diagram showing an example of a method for calculating the spiral pattern center position of the superimposed write spiral servo pattern according to the present embodiment.

Fig. 12 is a flowchart showing an example of the servo pattern writing method according to the present embodiment.

Fig. 13 is a flowchart showing an example of a servo pattern writing method according to the present embodiment.

Fig. 14 is a schematic diagram showing an example of a write processing method of an overlapping write-erase (erase) spiral pattern according to embodiment 2.

Fig. 15 is a schematic diagram showing an example of a table of offset amounts of the overlapping write/erase spiral patterns according to embodiment 2.

Fig. 16 is a schematic diagram showing an example of a write processing method of overlapping write/erase spiral patterns according to embodiment 2.

Fig. 17 is a schematic diagram showing an example of a write processing method of overlapping write/erase spiral patterns according to embodiment 2.

Fig. 18 is a schematic diagram showing an example of a method for calculating the center position of an erase pattern of the overlapping write erase spiral pattern according to embodiment 2.

Fig. 19 is a flowchart showing an example of a servo pattern writing method according to embodiment 2.

Fig. 20 is a flowchart showing an example of a servo pattern writing method according to embodiment 2.

Description of the reference numerals

1 a magnetic disk device; 10 magnetic disks; 10a user data area; 10b system area (system area); 12 spindle motor (SPM); 13 arm (arm); a 14 Voice Coil Motor (VCM); 15 heads; a 15W write head; 15R read head; 20 driver ICs; a 30-head amplifier IC;40 read/write (R/W) channels; a 50 Hard Disk Controller (HDC); 60 Microprocessors (MPUs); 70 volatile memory; 80 a non-volatile memory; a 90 buffer memory; 100 host systems (hosts); 130 a system controller.

Detailed Description

Hereinafter, embodiments will be described with reference to the drawings. The drawings are examples, and do not limit the scope of the invention.

(embodiment 1)

Fig. 1 is a block diagram showing a configuration of a magnetic disk device 1 according to embodiment 1.

The magnetic disk apparatus 1 includes a Head Disk Assembly (HDA) described later, a driver IC20, a head amplifier integrated circuit (hereinafter, head amplifier IC or preamplifier) 30, a volatile memory 70, a nonvolatile memory 80, a buffer memory (cache) 90, and a system controller 130 as a single-chip integrated circuit. The disk device 1 is connected to a host system (hereinafter, simply referred to as a host) 100.

The HDA includes a magnetic disk (hereinafter referred to as a disk) 10, a spindle motor (hereinafter referred to as an SPM) 12, an arm 13 on which a head 15 is mounted, and a voice coil motor (hereinafter referred to as a VCM) 14. The disk 10 is mounted on the SPM12, and is rotated by driving of the SPM 12. The arm 13 and the VCM14 constitute an actuator. The actuator controls the movement of the head 15 mounted on the arm 13 to a predetermined position of the disk 10 by the driving of the VCM 14. The disk 10 and the head 15 may be provided in two or more numbers. In addition, two or more actuators may be provided as well.

The disc 10 is allocated with a user data area 10a that can be utilized by a user and a system area 10b that writes information necessary for system management in an area where data can be written. In addition, a medium cache (or, sometimes, a medium cache area) for temporarily storing or recording data (or instructions) transferred from the host 100 or the like before writing them into a predetermined area of the user data area 10a may be allocated as an area different from the user data area 10a and the system area 10b in the disk 10. Hereinafter, a direction from the inner periphery of the disk 10 toward the outer periphery or a direction from the outer periphery of the disk 10 toward the inner periphery is referred to as a radial direction. In the radial direction, the direction from the inner periphery toward the outer periphery is referred to as the outer direction (or the outer side), and the direction from the outer periphery toward the inner periphery is referred to as the inner direction (or the inner side). A direction intersecting, for example, orthogonal to the radial direction of the disk 10 is referred to as a circumferential direction. The circumferential direction corresponds to a direction along the circumference of the disk 10. The predetermined position in the radial direction of the disk 10 may be referred to as a radial position, and the predetermined position in the circumferential direction of the disk 10 may be referred to as a circumferential position. The radial position and the circumferential position are also collectively referred to as simply a position. The disk 10 is divided into a plurality of areas (hereinafter, also referred to as zones (zones) or partitioned areas) for each predetermined range in the radial direction. The partition includes a plurality of tracks (tracks). The track includes a plurality of sectors (sectors). Further, the "track" is used in various meanings such as "one of a plurality of areas obtained by dividing the disk 10 in the radial direction by each predetermined range", "data written to one of a plurality of areas obtained by dividing the disk 10 in the radial direction by each predetermined range", "an area extending in the circumferential direction at a predetermined radial position of the disk 10", "data written to an area extending in the circumferential direction at a predetermined radial position of the disk 10", "an area around a predetermined radial position of the disk 10", "data written to an amount around an area around a predetermined radial position of the disk 10", "a path of the head 15 written while being positioned at a predetermined radial position of the disk 10", "data written to a predetermined track of the disk 10", and other various meanings. The "sector" is used in various meanings such as "one of a plurality of areas obtained by dividing a predetermined track of the disk 10 in the circumferential direction", "data written to one of a plurality of areas obtained by dividing a predetermined track of the disk 10 in the circumferential direction", "an area of a predetermined circumferential position at a predetermined radial position of the disk 10", "data written to a predetermined sector of the disk 10", and other various meanings. The "width in the radial direction of the track" is also sometimes referred to as "track width". The "center position of the track width" is also sometimes referred to as "track center". The "track center" is also sometimes simply referred to as "track".

The head 15 is composed mainly of a slider, and includes a write head 15W and a read head 15R attached to the slider. The write head 15W writes data to the disk 10. For example, the write head 15W writes a predetermined track on the disk 10. The read head 15R reads data recorded in the disk 10. For example, the read head 15R reads a predetermined track of the disk 10. In addition, the "write head 15W" is sometimes simply referred to as "head 15", and the "read head 15R" is sometimes simply referred to as "head 15". In addition, "write head 15W and read head 15R" are sometimes collectively referred to as "head 15". The "center portion of the head 15" is sometimes referred to as "head 15", the "center portion of the write head 15W" is sometimes referred to as "write head 15W", and the "center portion of the read head 15R" is sometimes referred to as "read head 15R". The "center portion of the write head 15W" is sometimes simply referred to as "head 15", and the "center portion of the read head 15R" is sometimes simply referred to as "head 15". The expression "positioning the center portion of the head 15 at a predetermined position" may be expressed by "positioning the head 15 at a predetermined position", "disposing the head 15 at a predetermined position", or "positioning the head 15 at a predetermined position", or the like.

Fig. 2 is a schematic diagram showing an example of the arrangement of the head 15 with respect to the disk 10 according to the present embodiment. In fig. 2, the innermost peripheral IMC and outermost peripheral OMC of the disc 10 are shown. As shown in fig. 2, in the circumferential direction, the direction in which the disk 10 rotates is referred to as a rotation direction. In the example shown in fig. 2, the rotation direction is shown in the counterclockwise direction, but may be the reverse direction (clockwise direction).

In the example shown in fig. 2, in the disk 10, the system area 10b is arranged in the outer direction of the user data area 10 a. In other words, in the disk 10, the user data area 10a is disposed in the inner direction of the system area 10 b. In the example shown in fig. 2, the system area 10b is arranged at the outermost periphery OMC of the disk 10. The user data area 10a may be divided and arranged in the radial direction of the disk 10. The system area 10b may be disposed at a position different from the position shown in fig. 2. For example, the system area 10b may be disposed between a plurality of user data areas 10a in the disk 10, or may be disposed at the innermost IMC of the disk 10.

The disk 10 has a data area DA, a plurality of servo patterns (hereinafter, also referred to as product servo patterns) or a plurality of servo areas (hereinafter, also referred to as product servo areas) PSV used in the Final product, and a plurality of Spiral servo patterns (a plurality of coarse lead Spiral (CGS: coarse Guide Spiral) servo patterns, a plurality of fine lead Spiral (FGS: fine Guide Spiral) servo patterns, and a plurality of Final Spiral (FS: final Spiral) servo patterns) SSP, which are different from the plurality of product servo patterns PSV.

In fig. 2, a plurality of data areas DA are respectively disposed between a plurality of product servo patterns PSV. For example, the data area DA corresponds to an area between two consecutive product servo patterns PSV in the circumferential direction. In addition, the "one data area DA on a predetermined track" is also sometimes referred to as a "data sector area". That is, the data area DA has at least one data sector area. The "data area DA" is also sometimes referred to as "data sector area DA". The data sector area has at least one sector. The "data sector area" is also sometimes referred to as a "sector". The "data written to the data sector area" is also sometimes referred to as a "data sector area". In addition, "data other than the product servo data written to the data sector area" is sometimes referred to as "user data".

In fig. 2, a plurality of spiral servo patterns SSP are spirally elongated on the disk 10 for convenience. Although the plurality of spiral servo patterns SSP are described as extending in parallel on the disk 10, they may not be actually extending in parallel. The plurality of spiral servo patterns SSP are discretely arranged at predetermined intervals in the circumferential direction of the disk 10. Hereinafter, the "spiral servo pattern SSP on a predetermined track" is sometimes referred to as a "spiral servo sector". In addition, the "spiral servo pattern SSP" is sometimes referred to as a "spiral servo sector". The "spiral servo sectors" are also sometimes referred to as "spiral servo patterns". The "spiral servo sectors" contain corresponding "servo data". In addition, the "spiral servo data written to a spiral servo sector" is sometimes referred to as a "spiral servo sector" or a "spiral servo pattern". In addition, "servo data" is sometimes referred to as "servo sector" or "servo pattern".

In fig. 2, for convenience, a plurality of product servo patterns PSV are linearly elongated in a radial direction. In addition, the plurality of product servo patterns PSV are described as extending linearly from the inside to the outside in the radial direction, but may be curved. For example, the product servo pattern PSV may also extend helically over the disk 10. The plurality of product servo patterns PSV extend radially in the radial direction of the disk 10, and are arranged discretely at predetermined intervals in the circumferential direction of the disk 10. Hereinafter, the "product servo pattern PSV on a predetermined track" may be referred to as a "product servo sector". In addition, the "product servo pattern PSV" is also sometimes referred to as a "product servo sector". The "product servo sector" is also sometimes referred to as a "product servo pattern". The product servo sectors contain servo data. In addition, the "product servo data written to the product servo sector" is sometimes referred to as a "product servo sector".

The servo sector (or servo data) contains, for example, a Preamble (Preamble) and a synchronization mark. In the servo sector, the preamble and the Sync Mark (or Sync field data Mark) (Sync Mark) are arranged sequentially from front to back in their circumferential direction. The preamble includes preamble information for synchronizing with a reproduction signal of a servo pattern composed of servo marks, gray codes, and the like. The sync mark contains information for detecting the beginning of a data sector area or the like. The servo sectors may also contain data other than the preamble and the sync mark. In addition, a sync mark may be included in the data sector area.

The driver IC20 is connected to a system controller 130 (specifically, an MPU60 described later), the SPM12, and the VCM14, and controls driving of the SPM12 and the VCM14 under control of the system controller 130 (specifically, the MPU60 described later).

The head amplifier IC (pre-amplifier) 30 includes a read amplifier, a write driver, and the like. The read amplifier amplifies a read signal read from the disk 10 and outputs the amplified read signal to a system controller 130 (specifically, a read/write (R/W) channel 40 described later). The write driver outputs a write current corresponding to the signal output from the R/W channel 40 to the head 15. The head amplifier IC30 is electrically connected to the head 15 and the like.

The volatile memory 70 is a semiconductor memory that loses stored data when the power supply is turned off. The volatile memory 70 stores data and the like necessary for processing in each section of the disk device 1. The volatile memory 70 is, for example, a DRAM (Dynamic Random Access Memory ) or an SDRAM (Synchronous Dynamic Random Access Memory, synchronous dynamic random access memory). The volatile memory 70 may be included in a system controller 130 described later.

The nonvolatile memory 80 is a semiconductor memory that records stored data even when the power supply is turned off. The nonvolatile memory 80 is, for example, a NOR-type or NAND-type flash memory (Flash Read Only Memory: FROM, flash read only memory). The nonvolatile memory 80 may be included in a system controller 130 described later.

The buffer memory 90 is a semiconductor memory that temporarily records data and the like transmitted/received (transmitted/received) between the disk device 1 and the host 100. The buffer memory 90 may be integrally formed with the volatile memory 70. The buffer memory 90 is, for example, a DRAM, an SRAM (Static Random Access Memory ), an SDRAM, an FeRAM (Ferroelectric Random Access memory, ferroelectric random access memory), an MRAM (Magnetoresistive Random Access Memory ), or the like. The buffer memory 90 may be included in a system controller 130 described later.

The System controller (controller) 130 is implemented using, for example, a large-scale integrated circuit (LSI) called a System-on-a-Chip (Soc) in which a plurality of elements are integrated on a single Chip. The system controller 130 includes a read/write (R/W) channel 40, a Hard Disk Controller (HDC) 50, and a Microprocessor (MPU) 60. The R/W channel 40, the HDC50 and the MPU60 are electrically connected to each other, respectively. The system controller 130 is electrically connected to, for example, the driver IC20, the head amplifier IC30, the volatile memory 70, the nonvolatile memory 80, the buffer memory 90, the host system 100, and the like.

The R/W channel 40 performs signal processing of data transferred from the disk 10 to the host 100, such as read data, and data transferred from the host 100, such as write data, in accordance with an instruction from the MPU60 described later. The R/W channel 40 is electrically connected to, for example, the head amplifier IC30, the HDC50, the MPU60, and the like. The R/W channel 40 has a circuit or function for modulating write data. The R/W channel 40 has a circuit or function for measuring the signal quality of read data and a circuit or function for decoding read data. The R/W channel 40 is electrically connected to the head amplifier IC30 and the like.

The HDC50 controls the transfer of data. The HDC50 controls data transfer between the host 100 and the disk 10 in accordance with an instruction from the MPU60 described later. The HDC50 is electrically connected to, for example, the head amplifier IC30, the R/W channel 40, the MPU60, the volatile memory 70, the nonvolatile memory 80, the buffer memory 90, and the like.

The MPU60 is a main controller that controls each part of the disk apparatus 1. The MPU60 controls the VCM14 via the driver IC20, and performs servo control for positioning the head 15. The MPU60 controls the SPM12 via the driver IC20 to rotate the disk 10. The MPU60 controls a writing operation (work) of writing data to the disk 10, and selects data transferred from the host 100, for example, a save destination of the write data. The MPU60 controls a reading action of reading data from the disk 10, and controls processing of data transferred from the disk 10 to the host 100, for example, reading data. In addition, the MPU60 manages an area in which data is recorded. The MPU60 is connected to each part of the magnetic disk apparatus 1. The MPU60 is electrically connected to, for example, the driver IC20, the R/W channel 40, the HDC50, and the like.

The MPU60 includes a read/write control unit 610, a servo pattern writing unit 620, and a positioning control unit 630. The MPU60 executes processing of each of these parts, for example, the read/write control part 610, the servo pattern writing part 620, the positioning control part 630, and the like, on firmware. The MPU60 may include, as circuits, respective parts such as a read/write control unit 610, a servo pattern writing unit 620, and a positioning control unit 630.

The read/write control unit 610 controls the read processing and write processing of data in accordance with an instruction or the like from the host 100. The read/write control unit 610 controls the VCM14 via the driver IC20, and disposes the head 15 at a predetermined radial position on the disk 10 to execute a read process or a write process. Hereinafter, the term "write process" and "read process" may be collectively referred to as "access" or "access process".

The servo pattern writing section 620 writes a servo pattern to the disk 10. The servo pattern writing part 620 writes the spiral servo pattern SSP and the product servo pattern PSV to the disk 10.

The servo pattern writing part 620 writes a spiral servo pattern SSP to the disk 10. The servo pattern writing unit 620 writes the spiral servo pattern SSP at a predetermined speed (hereinafter, also referred to as a spiral speed) in a step of sequentially writing Blank Disk Writing (BDW) (or blank disk servo writing) (hereinafter, also referred to as a BDW step) of writing data and patterns (hereinafter, also referred to as a blank state) to the disk 10 in which no data and patterns are written at all (hereinafter, also referred to as a blank state). In the BDW process, the servo pattern writing unit 620 does not perform a reading process (or on-track) because data, a pattern, or the like cannot be read from the disk 10 in a blank state, but uses the position of the disk 10 corresponding to the reference clock (hereinafter, also referred to as clock reference position) 1 time in 1 week of the disk 10 in a blank state as a start point, and performs constant speed control of the head 15 at a predetermined spiral speed based on speed information (hereinafter, also referred to as back electromotive force speed information) of the head 15 with respect to the disk 10 based on back electromotive force generated from the VCM14, so as to write the spiral servo pattern SSP from the inner direction, for example, the innermost circumference IMC toward the outer direction, for example, the outermost circumference OMC of the disk 10 in the radial direction. In the BDW process, the servo pattern writing unit 620 may perform constant speed control on the head 15 at a predetermined spiral speed based on the back electromotive force speed information with the clock reference position of the disk 10 in a blank state as a start point, and write the spiral servo pattern SSP on the disk 10 from the radially outer direction, for example, the outermost circumference OMC toward the inner direction, for example, the innermost circumference IMC.

The servo pattern writing unit 620 writes the spiral servo pattern SSP while accelerating the head 15 until reaching a predetermined spiral velocity in a range from a start point, that is, a clock reference position, to a position where the constant velocity control of the head 15 is started in the disk 10 in a blank state. When the head 15 reaches the position where the constant speed control of the head 15 is started, the servo pattern writing unit 620 writes the spiral servo pattern SSP by performing constant speed control of the head 15 at a predetermined spiral speed in a range from the position where the constant speed control of the head 15 is started to the position where the deceleration of the head 15 is started in the blank disk 10. When the head 15 reaches the position where the deceleration of the head 15 is started, the servo pattern writing unit 620 writes the spiral servo pattern SSP while decelerating the head 15 from the predetermined speed to the predetermined speed in a range from the position where the deceleration is started to the end point of the disk 10 in the blank state. Hereinafter, the state in which the head 15 is accelerated until the predetermined speed is reached in a range from the start point to the position where the constant speed control of the head 15 is started is also referred to as an acceleration state, acceleration time, acceleration control, or acceleration control, the state in which the head 15 is written at the constant speed is referred to as a constant speed state, constant speed time, constant speed control, or constant speed control, and the state in which the head 15 is decelerated until the predetermined speed is reached in a range from the position where the deceleration of the head 15 is started to the end point is referred to as a deceleration state, deceleration time, or deceleration control. In addition, the "speed at constant speed of the head 15 for writing a spiral servo pattern" may be referred to as the "spiral speed", the "speed at acceleration of the head 15 for writing a spiral servo pattern" may be referred to as the "spiral speed", and the "speed at deceleration of the head 15 for writing a spiral servo pattern" may be referred to as the "spiral speed". In addition, "the speed of the head 15 (at the time of acceleration, at the time of constant speed, and at the time of deceleration) to which the spiral servo pattern is written" is also sometimes collectively referred to as "spiral speed".

The servo pattern writing section 620 superimposes and writes a plurality of spiral servo patterns SSP on the disk 10. In other words, the servo pattern writing unit 620 superimposes and writes another spiral servo pattern (hereinafter, also simply referred to as another spiral servo pattern) SSP different from the predetermined spiral servo pattern SSP on a part of the disk 10 in the radial direction. The servo pattern writing unit 620 may overwrite other spiral servo patterns SSP without being offset (shifted) from the predetermined spiral servo patterns SSP, as long as the servo patterns are not overwritten on the identical tracks in the disk 10, that is, if the servo patterns are slightly offset (shifted). Hereinafter, the "multiple spiral servo patterns to be superimposed" may be referred to as "superimposed spiral servo patterns", or simply "spiral servo patterns". In addition, the "spiral servo pattern which is not written in a superimposed manner" and the "one spiral servo pattern" are sometimes referred to as "normal spiral servo pattern" or simply "spiral servo pattern". The servo pattern writing unit 620 may write the spiral servo pattern overlapping the entire surface of the disk 10. In addition, the servo pattern writing section 620 may write an overlapping write spiral servo pattern to a portion of the disk 10. In other words, the servo pattern writing section 620 may write the overlapping write spiral servo pattern and the normal spiral servo pattern in a mixed manner to the disk 10.

For example, the width of the spiral servo pattern SSP is generally smaller than the width of the overlap-written spiral servo pattern SSP. In other words, the width of the overlap-written spiral servo pattern SSP is larger than that of the normal spiral servo pattern SSP. The width of the spiral servo pattern SSP is generally comparable to the width of the write head 15W, for example. The width of the spiral servo pattern SSP may be smaller than the width of the write head 15W, and may be larger than the width of the write head 15W. The width of the overlap written spiral servo pattern SSP is, for example, greater than the width of the write head 15W. The width of the superimposed write spiral servo pattern SSP may be smaller than the width of the write head 15W, or may be the same as the width of the write head 15W, for example.

The servo pattern writing unit 620 superimposes and writes a plurality of spiral servo patterns (normally spiral servo patterns) SSP on the disk 10 in a blank state. The servo pattern writing unit 620 writes a plurality of spiral servo patterns SSP in the disk 10 in a blank state by overlapping the spiral servo patterns SSP with each other in one direction (hereinafter, also referred to as a forward direction) such as a radial direction. The servo pattern writing unit 620 writes a plurality of spiral patterns (normal spiral servo patterns) SSP in the disk 10 in a blank state by overlapping the spiral patterns SSP with each other at a predetermined interval (hereinafter, also referred to as offset) so as to be shifted in the radial direction. Hereinafter, one direction in which a plurality of spiral servo patterns (normal spiral servo patterns) SSP are superimposed is sometimes referred to as a forward direction. That is, the forward direction corresponds to a direction in which a different spiral servo pattern is superimposed and written on a part of a predetermined spiral servo pattern. In the case of writing the superimposed spiral servo pattern SSP, the servo pattern writing unit 620 may write (or overwrite) each normal spiral servo pattern in the superimposed spiral servo pattern at the same position by repeating the pattern a predetermined number of times (hereinafter, may be referred to as the number of repetitions).

For example, the servo pattern writing unit 620 writes 3 spiral servo patterns SSP in a superimposed manner with 0.5 tracks being shifted in the normal direction in the disk 10 in a blank state, and writes the superimposed spiral servo patterns SSP. The servo pattern writing unit 620 may write the superimposed spiral servo pattern SSP by superimposing and writing 2 spiral servo patterns SSP with 0.5 track being shifted in the forward direction on the disk 10 in the blank state, or may write the superimposed spiral servo pattern SSP by superimposing and writing 4 or more spiral servo patterns SSP with 0.5 track being shifted in the forward direction on the disk 10 in the blank state. The spiral servo pattern SSP is not limited to 0.5 tracks in the range where the written spiral servo pattern SSP overlaps, and may be written by overlapping the spiral servo patterns SSP with any offset in the range of 0 to 1.

The servo pattern writing unit 620 calculates or obtains a center position of the width of the spiral servo pattern SSP (hereinafter, also referred to as a spiral pattern center position). The servo pattern writing unit 620 acquires a demodulated MAG value every time a Sync mark (Sync) of a read signal (or read signal intensity) of the spiral servo pattern SSP is detected, and calculates or acquires a position corresponding to a timing (timing) corresponding to half (1/2) of an integrated value (hereinafter, also simply referred to as an integrated value) of the demodulated MAG value as a spiral pattern center position. Demodulating the MAG value corresponds to the value associated with the read signal. Demodulating the MAG value corresponds to, for example, a signal level or area.

For example, the servo pattern writing unit 620 acquires the demodulated MAG value every time the sync mark of the normal spiral servo pattern SSP is detected, and calculates or acquires a position corresponding to a timing corresponding to half (1/2) of the integrated value of the demodulated MAG value as the spiral pattern center position.

For example, the servo pattern writing unit 620 acquires a demodulated MAG value every time a sync mark overlapping the written spiral servo pattern SSP is detected, and calculates or acquires a position corresponding to a timing corresponding to half (1/2) of the integrated value of the demodulated MAG value as the spiral pattern center position.

The servo pattern writing section 620 writes the product servo pattern PSV to the disk 10. The servo pattern writing unit 620 writes the product servo pattern PSV based on the spiral servo pattern SSP in a self-servo writing (SSW) process (hereinafter, also referred to as SSW process or SSW process). In the SSW step, the servo pattern writing unit 620 writes the product servo pattern PSV from the radially inner direction, for example, the innermost circumference IMC toward the outer direction, for example, the outermost circumference OMC, based on the spiral servo pattern SSP and the spiral pattern center position, while correcting the deviation of the spiral pattern center position by using the position error calculation. In the SSW step, the servo pattern writing unit 620 may write the product servo pattern PSV from the radially outer direction, for example, the outermost circumference OMC toward the inner direction, for example, the innermost circumference IMC, based on the spiral servo pattern SSP and the spiral pattern center position, while correcting the deviation of the spiral pattern center position by using the position error calculation. In addition, the BDW process and the SSW process are sometimes collectively referred to as the SSW process. The servo pattern writing unit 620 may write the spiral servo pattern SSP in the SSW process.

The positioning control section 630 performs positioning control of the head 15. The positioning control section 630 performs positioning control of the head 15 based on the spiral servo pattern SSP, the spiral pattern center position, and the product servo pattern PSV. The positioning control section 630 calculates a position error based on the spiral pattern center position, and performs positioning control of the head 15 based on the position error. In other words, the MPU60 calculates a position error using the deviation of the spiral pattern center position, and performs positioning control of the head 15 based on the calculated position error.

Fig. 3 is a schematic diagram showing an example of a write signal of the spiral servo pattern SSP. In fig. 3, the horizontal axis represents time. The time on the horizontal axis in fig. 3 passes as it goes toward the tip end side of the arrow.

The MPU60 writes the spiral servo pattern SSP by alternately writing basic Dibit (double bit) and Sync marks (Sync) to the disk 10 in accordance with a write signal of the spiral servo pattern SSP as shown in fig. 3, for example.

Fig. 4 is a schematic diagram showing an example of a write processing method of the normal spiral servo pattern SSP. Fig. 4 shows the radial direction and the direction (hereinafter, also referred to as the time direction) along with the passage of time during writing of the spiral servo pattern SSP. The radial direction of fig. 4 proceeds in the outward direction as proceeding toward the front end side of the arrow, and proceeds in the inward direction as proceeding toward the opposite side of the front end side of the arrow. Fig. 4 shows normal spiral servo patterns SSPe1 (SSP), SSPe2 (SSP), and SSPe3 (SSP) arranged continuously at predetermined intervals on the disk 10. In the normal spiral servo patterns SSPe1 (SSP), SSPe2 (SSP), and SSPe3 (SSP) of fig. 4, the vertical lines correspond to synchronization marks (Sync). In the example shown in FIG. 4, the widths of the spiral servo patterns SSPe1, SSPe2, and SSPe3 generally correspond to the width of the write head 15W. Fig. 4 shows an ORRe of the read head 15R in the on-track state with respect to the path (hereinafter, also referred to as an on-track path) of the normal spiral servo patterns SSP (SSPe 1, SSPe2, and SSPe 3). In fig. 4, for convenience of explanation, the normal spiral servo patterns SSPe1 (SSP), SSPe2 (SSP), and SSPe3 (SSP) are shown to extend obliquely in a stripe shape, but may be actually arranged in a spiral shape on the disk 10. In fig. 4, the magnitudes of read signals or read signal intensities (hereinafter, also referred to as on-track read signal intensities) RSe, RSe, and RSe in the case where the normal spiral servo patterns SSP (SSPe 1, SSPe2, and SSPe 3) are read by the on-track read head 15R are shown. The time is shown in fig. 4. The time of fig. 4 passes as it goes toward the tip end side of the arrow. The on-track read signal strength RSe corresponds to the magnitude of a signal read by the on-track (or arranged on a predetermined track) read head 15R in the normal spiral servo pattern SSPe 1. The on-track read signal strength RSe corresponds to the magnitude of the signal read by the on-track read head 15R from the normal spiral servo pattern SSPe 2. The on-track read signal strength RSe corresponds to the magnitude of the signal read by the on-track read head 15R from the normal spiral servo pattern SSPe 3. In the read signal intensities RSe, RSe, and RSe31 at the time of on-track, the vertical line corresponds to the read signal intensity at which the synchronization mark (Sync) is read.

In the example shown in fig. 4, the MPU60 writes the normal spiral servo patterns SSPe1, SSPe2, and SSPe3 to the disk 10 at intervals in the time direction. The MPU60 reads the normal spiral servo patterns SSPe1, SSPe2, and SSPe3 by bringing the head 15R on the track according to the on-track path ORRe, and obtains on-track read signal intensities RSe, RSe21, and RSe31.

Fig. 5 is a schematic diagram showing an example of a write processing method of a normal spiral servo pattern. Fig. 5 shows the general spiral servo patterns SSPe1 (SSP), SSPe2 (SSP), and SSPe3 (SSP) shown in fig. 4. Fig. 5 shows a path (hereinafter, also referred to as a seek path) SRRe of the head 15R with respect to the normal spiral servo patterns SSP (SSPe 1, SSPe2, and SSPe 3) at the time of seek. In fig. 5, read signal intensities (hereinafter, sometimes referred to as seek-time read signal intensities) RSe, RSe, 22, and RSe32 in the case where the normal spiral servo patterns SSP (SSPe 1, SSPe2, and SSPe 3) are read by the seek head 15R are shown. The read signal intensity RSe at the time of seek corresponds to the magnitude of the signal read by the spiral servo pattern SSPe1 by the head 15R being seeking. The read signal intensity RSe at the time of seek corresponds to the magnitude of the signal read by the spiral servo pattern SSPe2 by the head 15R being seeking. The read signal intensity RSe at the time of seek corresponds to the magnitude of the signal read by the spiral servo pattern SSPe3 by the head 15R being seeking.

In the example shown in fig. 5, the MPU60 seeks the head 15R according to the seek path SRRe to read the normal spiral servo patterns SSPe1, SSPe2, and SSPe3, and obtains the read signal intensities RSe, RSe22, and RSe at the time of seek.

In the example shown in fig. 5, the read signal intensities RSe, RSe22, and RSe32 at seek are smaller than the read signal intensities RSe, RSe21, and RSe31 at track, and thus the number of synchronization marks (syncs) read by the on-track readhead 15R is smaller than the number of synchronization marks (syncs) read by the on-track readhead 15R.

Fig. 6 is a schematic diagram showing an example of a write processing method of the superimposed write spiral servo pattern SSP1 according to the present embodiment. The radial direction and the time direction are shown in fig. 6. In fig. 6, the forward direction corresponds to the outward direction. The forward direction may be the inner direction, or may be a direction other than the inner direction and the outer direction. Fig. 6 shows an overlapping write spiral servo pattern SSP1 (SSP). In fig. 6, for example, the superimposed spiral servo pattern SSP1 is formed by superimposed writing of normal spiral servo patterns SSP11, SSP12, and SSP13 in the order described. In other words, the overlay-written spiral servo pattern SSP1 includes normal spiral servo patterns SSP11, SSP12, and SSP13. In the normal spiral servo patterns SSP11, SSP12, and SSP13 shown in fig. 6, the vertical lines correspond to synchronization marks (Sync). In fig. 6, for convenience of explanation, the spiral servo patterns SSP1 (SSP) are shown as being overlapped and written, and the normal spiral servo patterns SSP11, SSP12, and SSP13 extend obliquely in a stripe shape, but may be actually arranged in a spiral shape on the disk 10.

In the example shown in fig. 6, the MPU60 writes a normal spiral servo pattern SSP11 to the disk 10 at a predetermined spiral speed. After writing the normal spiral servo pattern SSP11, the MPU60 staggers a predetermined offset in the forward direction with respect to the normal spiral servo pattern SSP11 and superimposes the normal spiral servo pattern SSP12 at a predetermined spiral speed. After the normal spiral servo pattern SSP12 is superimposed and written on the normal spiral servo pattern SSP11, the MPU60 writes the superimposed and written spiral servo pattern SSP1 by shifting the normal spiral servo pattern SSP12 by a predetermined shift amount in the forward direction and superimposed and written on the normal spiral servo pattern SSP13 at a predetermined spiral speed.

Fig. 7 is a schematic diagram showing an example of a table TB1 of offset amounts of the overlapped writing spiral servo patterns according to the present embodiment. Fig. 7 shows a table TB1 of offset values corresponding to the superimposed spiral servo pattern SSP1 shown in fig. 6. The table TB1 contains numbers corresponding to the order of overlapping the spiral servo patterns to be written in the overlapping spiral servo patterns (hereinafter, also referred to as overlapping write numbers), the offset amount of the spiral servo pattern SSP1 with respect to the overlapping write number 1, and the number of repetitions of each spiral servo pattern SSP. The table TB1 may be recorded in a predetermined recording area, for example, the disk 10, the volatile memory 70, the nonvolatile memory 80, or the buffer memory 90.

In the example shown in fig. 7, after writing the normal spiral servo pattern SSP11, the MPU60 staggers by-0.5 tracks (Track) in the forward direction with respect to the normal spiral servo pattern SSP11 and superimposes the normal spiral servo pattern SSP12 at a predetermined spiral speed as shown in table TB 1. After the normal spiral servo pattern SSP12 is superimposed and written on the normal spiral servo pattern SSP11, the MPU60 writes the superimposed and written spiral servo pattern SSP1 by shifting-1.0 Track (Track) in the forward direction with respect to the normal spiral servo pattern SSP11 and superimposed and written the normal spiral servo pattern SSP13 on the normal spiral servo pattern SSP12 at a predetermined spiral speed.

Fig. 8 is a schematic diagram showing an example of a write processing method of the superimposed write spiral servo pattern according to the present embodiment. The radial direction, the forward direction and the time direction are shown in fig. 8. Fig. 8 shows overlapping write spiral servo patterns SSP1 (SSP), SSP2 (SSP), and SSP3 (SSP) arranged consecutively at predetermined intervals on the disk 10. In the superimposed write spiral servo patterns SSP1, SSP2, and SSP3 of fig. 8, the vertical lines correspond to synchronization marks (Sync). In fig. 8, the overlay-written spiral servo pattern SSP1 includes normal spiral servo patterns SSP11, SSP12, and SSP13. The overlay-written spiral servo pattern SSP2 includes normal spiral servo patterns SSP21, SSP22, and SSP23. The overlay-written spiral servo pattern SSP3 includes normal spiral servo patterns SSP31, SSP32, and SSP33. In the example shown in fig. 8, the widths of the normal spiral servo patterns SSP11, SSP12, SSP13, SSP21, SSP22, SSP23, SSP31, SSP32, and SSP33 correspond to the width of the write head 15W. In fig. 8, the on-track path ORR1 of the read head 15R at the time of on-track is shown with respect to the superimposed write spiral servo patterns SSP (SSP 1, SSP2, and SSP 3). In fig. 8, for convenience of explanation, the write spiral servo patterns SSP1 (SSP), SSP2 (SSP), and SSP3 (SSP) are shown as being overlapped and written obliquely in a stripe shape, but are actually arranged in a spiral shape on the disk 10. The read signal strengths RS11, RS21 and RS31 at the time of the track are shown in fig. 8. The time is shown in fig. 8. The on-track read signal strength RS11 corresponds to the size of a signal read by the on-track head 15R to the overlapping write spiral servo pattern SSP1. The on-track read signal strength RS21 corresponds to the size of a signal read by the on-track head 15R to the overlapping write spiral servo pattern SSP 2. The on-track read signal strength RS31 corresponds to the size of a signal read by the on-track head 15R to the overlapping write spiral servo pattern SSP 3. In the on-track read signal intensities RS11, RS21, and RS31, the vertical line corresponds to the read signal intensity at which the sync mark is read.

In the example shown in fig. 8, the MPU60 writes the normal spiral servo patterns SSP11, SSP12, and SSP13 on the disk 10 in a superimposed manner and writes the superimposed spiral servo pattern SSP1. The MPU60 writes the normal spiral servo patterns SSP21, SSP22, and SSP23 in the overlapped write spiral servo pattern SSP2 in the overlapped write normal spiral servo patterns SSP21, SSP22, and SSP23 in the sequential direction with intervals in the time direction from the overlapped write spiral servo pattern SSP1. The MPU60 writes the normal spiral servo patterns SSP31, SSP32, and SSP33 in the overlapped write spiral servo pattern SSP3 in the overlapped write spiral servo pattern SSP2 in the forward direction with an interval in the time direction.

In the example shown in fig. 8, the MPU60 reads the superimposed write spiral servo patterns SSP1, SSP2, and SSP3 by bringing the head 15R on the track along the track path ORR1, and obtains the on-track read signal intensities RS11, RS21, and RS31.

The read signal intensities RS11, RS21, and RS31 at the track are larger than the read signal intensities RSe, RSe, and RSe31 at the track, so that the number of Sync marks (Sync) of the superimposed written spiral servo pattern SSP is larger than the number of Sync marks (Sync) of the normal spiral servo pattern SSP read by the on-track read head 15R.

Fig. 9 is a schematic diagram showing an example of a write processing method of the superimposed write spiral servo pattern according to the present embodiment. Fig. 9 shows the superimposed write spiral servo patterns SSP1 (SSP), SSP2 (SSP), and SSP3 (SSP) shown in fig. 8. Fig. 9 shows the seek path SRR1 of the head 15R at the seek time with respect to the superimposed write spiral servo patterns SSP (SSP 1, SSP2, and SSP 3). The read signal strengths RS12, RS22 and RS32 at seek time are shown in fig. 9. The read signal strength RS12 at the time of seek corresponds to the size of a signal read by the head 15R that is seeking to the superimposed write spiral servo pattern SSP1. The read signal strength RS22 at the time of seek corresponds to the size of a signal read by the head 15R that is seeking to the superimposed write spiral servo pattern SSP2. The read signal strength RS32 at the time of seek corresponds to the size of a signal read by the head 15R that is seeking to the superimposed write spiral servo pattern SSP3.

In the example shown in fig. 9, the MPU60 reads the superimposed write spiral servo patterns SSP1, SSP2, and SSP3 while seeking the head 15R according to the seek path SRR1, and obtains the read signal intensities RS12, RS22, and RS32 at the time of seeking.

In the example shown in fig. 9, the read signal intensities RS12, RS22, and RS32 at the seek time are larger than the read signal intensities RSe, RSe22, and RSe at the seek time, and thus the number of synchronization marks (Sync) read from the overlapped write spiral servo pattern SSP by the read head 15R at the seek time is larger than the number of synchronization marks (Sync) read from the normal spiral servo pattern SSP by the read head 15R at the seek time.

Fig. 10 is a schematic diagram showing an example of a method for calculating the spiral pattern center position of the normal spiral servo pattern SSPe 1. The on-track read signal strength of the normal spiral servo pattern SSPe1, the on-track path ORRe, and the normal spiral servo pattern SSPe1 shown in fig. 4 are shown in fig. 10. In fig. 10, a demodulated MAG value corresponding to the on-track read signal strength RSe1 of the normal spiral servo pattern SSPe1 (hereinafter, also referred to as an on-track normal demodulated MAG value) and a cumulative value of the demodulated MAG values corresponding to the on-track normal demodulated MAG value (hereinafter, also referred to as an on-track normal cumulative value or cumulative value) are shown. The horizontal axis of the on-track typically demodulated MAG value and the on-track typically accumulated value is time.

In the example shown in fig. 10, the MPU60 obtains each on-track normal demodulation MAG value corresponding to each timing at which a synchronization mark (Sync) is detected, based on the on-track read signal strength of the normal spiral servo pattern SSPe 1. The MPU60 calculates an on-track normal integrated value by integrating on-track normal demodulation MAG values corresponding to the timings at which the sync mark is detected based on the acquired on-track read signal intensity of the normal spiral servo pattern SSPe1, and calculates or acquires a position corresponding to the timing of half (1/2) of the on-track normal integrated value as the spiral pattern center position of the normal spiral servo pattern SSPe 1. The MPU60 may record the calculated spiral pattern center position of the normal spiral servo pattern SSPe1 in a predetermined recording area, for example, the disk 10, the volatile memory 70, the nonvolatile memory 80, or the buffer memory 90.

Fig. 11 is a schematic diagram showing an example of a method for calculating the spiral pattern center position of the superimposed write spiral servo pattern SSP1 according to the present embodiment. Fig. 11 shows the overlap write spiral servo pattern SSP1, the on-track path ORR1, and the on-track read signal strength RS11 of the overlap write spiral servo pattern SSP1 shown in fig. 8. In fig. 11, a demodulated MAG value corresponding to the on-track read signal strength RS11 of the spiral servo pattern SSP1 (hereinafter, also referred to as an on-track overlap write demodulated MAG value) and a cumulative value of the demodulated MAG values corresponding to the on-track overlap write demodulated MAG value (hereinafter, also referred to as an on-track overlap write cumulative value or cumulative value) are shown. The horizontal axis of the on-track overlay write demodulation MAG value and the on-track overlay write accumulation value is time.

In the example shown in fig. 11, the MPU60 acquires each on-track overlap write demodulation MAG value corresponding to each timing at which a synchronization mark (Sync) is detected, based on the on-track read signal strength RS11 of the overlap write spiral servo pattern SSP 1. The MPU60 calculates an on-track overlap write cumulative value by accumulating the acquired on-track overlap write demodulation MAG values corresponding to the timings at which the sync marks are detected based on the on-track read signal strength RS11 of the overlap-write spiral servo pattern SSP1, and calculates or acquires a position corresponding to half (1/2) of the timing of the on-track overlap write cumulative value as the spiral pattern center position of the overlap-write spiral servo pattern SSP 1. The MPU60 may record the calculated spiral pattern center position of the overlapped writing spiral servo pattern SSP1 in a predetermined recording area, for example, the disk 10, the volatile memory 70, the nonvolatile memory 80, or the buffer memory 90.

The MPU60 writes a predetermined spiral servo pattern (normal spiral servo pattern) SSP (B1201) on the disk 10, and writes another spiral servo pattern (normal spiral servo pattern) SSP by overlapping the spiral servo pattern (normal spiral servo pattern) SSP with the predetermined offset in the forward direction (B1202). The MPU60 determines whether or not to write a spiral servo pattern (normal spiral servo pattern) SSP in an overlapping manner (B1203).

If it is determined that the spiral servo pattern SSP (normal spiral servo pattern) is to be superimposed (yes in B1203), the MPU60 proceeds to the process in B1202. When it is determined that the spiral servo pattern SSP (normal spiral servo pattern) is not to be written in a superimposed manner (no in B1203), the MPU60 ends the processing.

The MPU60 reads the spiral servo pattern SSP (B1301) and acquires each demodulated MAG value every time the sync mark of the read signal of the spiral servo pattern SSP is detected (B1302). The MPU60 calculates the cumulative value of the demodulated MAG value corresponding to the spiral servo pattern SSP (B1303), calculates the position corresponding to the timing corresponding to half (1/2) of the cumulative value of the demodulated MAG value as the spiral pattern center position (B1304), and ends the process.

According to the present embodiment, the magnetic disk device 1 writes a plurality of normal spiral servo patterns SSP in the disk 10 by overlapping and writing the normal spiral servo patterns SSP so as to be shifted in the forward direction. The disk device 1 acquires a demodulated MAG value every time it detects a sync mark of a read signal of the spiral servo pattern SSP, and calculates a position corresponding to a timing corresponding to half (1/2) of the integrated value of the demodulated MAG value as a spiral pattern center position. Therefore, even if the head 15 having a narrow writing width is written in the magnetic disk device 1, defects in the SSW process and the like can be reduced. Therefore, the magnetic disk apparatus 1 can improve reliability.

Next, a magnetic disk device according to another embodiment of embodiment 1 will be described. In other embodiments, the same reference numerals are given to the same parts as those in embodiment 1, and detailed description thereof is omitted.

(embodiment 2)

The magnetic disk device 1 according to embodiment 2 is different from the magnetic disk device 1 according to embodiment 1 in that the write processing method of the spiral servo pattern SSP is different.

The MPU60 writes an overlapped-writing spiral servo pattern SSP, and writes (or overwrites) an erase pattern to the overlapped-writing spiral servo pattern SSP. The MPU60 desirably writes (or overwrites) the erase pattern only once in the center portion of the width of the overlap-write spiral servo pattern SSP because both ends of the erase pattern in the width direction, for example, in the radial direction (hereinafter, also simply referred to as both ends of the erase pattern) have the same shape. The MPU60 may write (or overwrite) the erase pattern other than the center portion of the width of the superimposed spiral servo pattern SSP. In addition, the MPU60 may write (or overwrite) the erase pattern a plurality of times for overlapping the spiral servo pattern SSP. The erase pattern corresponds to an AC erase pattern having a frequency higher than that of predetermined data, for example, a normal spiral servo pattern. The erase pattern corresponds to an AC erase pattern having a frequency that is several times, for example, 4 times as high as that of a normal spiral servo pattern.

The MPU60 calculates or acquires a center position of a width of an erase pattern (hereinafter, also referred to as an erase pattern center position) of an overlap write spiral servo pattern SSP (hereinafter, also referred to as an overlap write erase spiral pattern) in which the erase pattern is overwritten. The MPU60 obtains a demodulation MAG value (hereinafter, also referred to as an erase spiral demodulation MAG value) every time it detects a Sync mark (Sync) that overlaps a read signal (or read signal strength) written in the erase spiral pattern SSP. The MPU60 calculates difference values (hereinafter, also referred to as erasure spiral difference values) between the largest erasure spiral demodulation MAG value (hereinafter, also referred to as maximum erasure spiral demodulation MAG value or demodulation MAG value) in the area not including the erasure pattern among the erasure spiral demodulation MAG values of the overlapping write erasure spiral pattern and each erasure spiral demodulation MAG value (hereinafter, also referred to as erasure demodulation MAG value or demodulation MAG value) in the area including the erasure pattern of the overlapping write erasure spiral pattern. The MPU60 calculates an integrated value (hereinafter, also referred to as a differential integrated value or an integrated value) obtained by integrating the respective erasure spiral differential values, and calculates or acquires a position corresponding to a timing corresponding to half (1/2) of the differential integrated value as an erasure pattern center position.

The MPU60 calculates a position error based on the erasing pattern center position, and performs positioning control of the head 15 based on the calculated position error. In other words, the MPU60 calculates a position error using the deviation of the erasing pattern center position, and performs positioning control of the head 15 based on the calculated position error.

Fig. 14 is a schematic diagram showing an example of a write processing method of the superimposed write/erase spiral pattern SSP4 according to the present embodiment. Fig. 14 shows the radial direction, the forward direction, and the time direction. In fig. 14, the forward direction corresponds to the outward direction. The forward direction may be the inner direction, or may be a direction other than the inner direction and the outer direction. Fig. 14 shows an overlapped write erase spiral pattern SSP4 (SSP). In fig. 14, for example, the overlap write erase spiral pattern SSP4 includes normal spiral servo patterns SSP41, SSP42, SSP43, SSP44, SSP45, and SSP46, and an erase pattern EP4. In the normal spiral servo patterns SSP41, SSP42, SSP43, SSP44, SSP45, and SSP46 shown in fig. 14, the vertical lines correspond to synchronization marks (Sync). In fig. 14, for convenience of explanation, the write-erase spiral pattern SSP4, the normal spiral servo patterns SSP41 to SSP46, and the erase pattern EP4 are shown as being overlapped, extending obliquely in a stripe shape, but may be actually arranged in a spiral shape on the disk 10.

In the example shown in fig. 14, the MPU60 writes a normal spiral servo pattern SSP41 to the disk 10 at a predetermined spiral speed. After writing the normal spiral servo pattern SSP41, the MPU60 staggers a predetermined offset in the forward direction with respect to the normal spiral servo pattern SSP41 and superimposes the normal spiral servo pattern SSP42 at a predetermined spiral speed. After the normal spiral servo pattern SSP42 is superimposed and written on the normal spiral servo pattern SSP41, the MPU60 shifts a predetermined shift amount in the forward direction with respect to the normal spiral servo pattern SSP42 and superimposes and writes the normal spiral servo pattern SSP43 at a predetermined spiral speed. After the normal spiral servo pattern SSP43 is superimposed and written on the normal spiral servo pattern SSP42, the MPU60 shifts a predetermined shift amount in the forward direction with respect to the normal spiral servo pattern SSP43 and superimposes and writes the normal spiral servo pattern SSP44 at a predetermined spiral speed. After the normal spiral servo pattern SSP44 is superimposed and written on the normal spiral servo pattern SSP43, the MPU60 shifts a predetermined shift amount in the forward direction with respect to the normal spiral servo pattern SSP44 and superimposes and writes the normal spiral servo pattern SSP45 at a predetermined spiral speed. After the normal spiral servo pattern SSP45 is superimposed on the normal spiral servo pattern SSP44, the MPU60 writes the superimposed spiral servo pattern by shifting the normal spiral servo pattern SSP45 by a predetermined shift amount in the forward direction and superimposed on the normal spiral servo pattern SSP46 at a predetermined spiral speed.

The MPU60 writes the overlapped write erase pattern SSP4 by overwriting the erase pattern EP4 in the central portion including the width of the overlapped write spiral servo patterns of the normal spiral servo patterns SSP41 to SSP 46.

Fig. 15 is a schematic diagram showing an example of table TB2 of offset amounts of the write-overlap erase spiral patterns according to embodiment 2. Fig. 15 shows a table TB2 of offset amounts corresponding to the overlap write erase spiral pattern SSP4 shown in fig. 14. The table TB2 contains the superimposed write number corresponding to the order of superimposed writing the spiral servo pattern in the superimposed writing and erasing spiral pattern, the offset amount of the spiral servo pattern SSP44 with respect to the superimposed write number No. 4, and the number of repetitions of each spiral servo pattern SSP. The table TB2 may be recorded in a predetermined recording area, for example, the disk 10, the volatile memory 70, the nonvolatile memory 80, or the buffer memory 90.

In the example shown in fig. 15, the MPU60 writes the spiral servo pattern SSP41 with a shift of +1.5 tracks (Track) from the position where the spiral servo pattern SSP44 is arranged in the opposite direction (hereinafter, may be referred to as the opposite direction). The MPU60 may repeatedly write (or overwrite) the spiral servo pattern SSP41 1 to 5 times.

The MPU60 writes the spiral servo pattern SSP42 overlapping the spiral servo pattern SSP41 in the forward direction by shifting the position where the spiral servo pattern SSP44 is arranged by +1.0 tracks (Track) in the reverse direction (hereinafter, may be referred to as the reverse direction). The MPU60 may repeatedly write (or overwrite) the spiral servo pattern SSP42 1 to 5 times.

The MPU60 writes the spiral servo pattern SSP43 overlapping the spiral servo pattern SSP42 in the forward direction while shifting +0.5 tracks (Track) in the reverse direction from the position where the spiral servo pattern SSP44 is disposed. The MPU60 may repeatedly write (or overwrite) the spiral servo pattern SSP43 1 to 5 times.

The MPU60 writes the spiral servo pattern SSP44 overlapping the spiral servo pattern SSP43 in the forward direction. The MPU60 may repeatedly write (or overwrite) the spiral servo pattern SSP44 1 to 5 times.

The MPU60 writes the spiral servo pattern SSP45 overlapping the spiral servo pattern SSP44 in the forward direction with a shift of-0.5 tracks (Track) from the position where the spiral servo pattern SSP44 is arranged. The MPU60 may repeatedly write (or overwrite) the spiral servo pattern SSP45 1 to 5 times.

The MPU60 writes the superimposed write spiral servo pattern including the spiral servo patterns SSP41 to SSP46 by shifting-1.0 tracks (Track) in the forward direction from the position where the spiral servo pattern SSP44 is arranged and superimposing the spiral servo pattern SSP46 in the forward direction with the spiral servo pattern SSP45. The MPU60 may repeatedly write (or overwrite) the spiral servo pattern SSP46 1 to 5 times.

The MPU60 writes the overlapped write/erase spiral pattern SSP4 by overlapping the erase pattern EP4 in the center portion of the width of the overlapped write spiral servo pattern including the spiral servo patterns SSP41 to SSP46 with 0.5 to 0 tracks (Track) shifted in the forward direction from the position where the spiral servo pattern SSP44 is arranged. The MPU60 overwrites the erase pattern EP4 only 1 time.

In addition, if the MPU60 can write without any gap even if the overlapping writing accuracy is not sufficiently obtained, the spiral servo patterns SSP41 to SSP46 may be repeatedly overlapped or rewritten 6 times or more, respectively. The MPU60 may write the superimposed spiral servo pattern by superimposing and writing 5 or less spiral servo patterns SSP, or may write the superimposed spiral servo pattern by superimposing and writing 7 or more spiral servo patterns SSP.

Fig. 16 is a schematic diagram showing an example of a write processing method of overlapping write/erase spiral patterns according to embodiment 2. Fig. 16 shows the radial direction, the forward direction, and the time direction. Fig. 16 shows overlapping write erase spiral patterns SSP4 (SSP) and SSP5 (SSP) arranged consecutively at predetermined intervals on the disk 10. In the overlapped write erase spiral patterns SSP4 and SSP5 of fig. 16, the vertical lines correspond to synchronization marks (Sync). In fig. 16, the overlay write erase spiral pattern SSP4 includes spiral servo patterns SSP41, SSP42, SSP43, SSP45, SSP46, and erase pattern EP4. The overlap write erase spiral pattern SSP5 includes spiral servo patterns SSP51, SSP52, SSP53, SSP55, SSP56, and an erase pattern EP5. In the example shown in fig. 16, the widths of the spiral servo patterns SSP41, SSP42, SSP43, SSP45, SSP46, SSP51, SSP52, SSP53, SSP55, SSP56, and erase patterns EP4 and EP5 correspond to the width of the write head 15W. Fig. 16 shows an on-track path ORR2 of the read head 15R in the on-track process with respect to the overlap write erase spiral patterns SSP (SSP 4 and SSP 5). In fig. 16, for convenience of explanation, the write-erase spiral patterns SSP4 (SSP) and SSP5 (SSP) are shown as being overlapped and obliquely extending in a stripe shape, but may be actually arranged in a spiral shape on the disk 10. The on-track read signal strengths RS41, RS42, RS51 and RS52 are shown in fig. 16. The time is shown in fig. 16. The read signal intensities RS41 and RS42 at the time of the track correspond to the magnitude of the signal read by the on-track head 15R to the overwrite erase spiral pattern SSP4. The read signal intensities RS51 and RS52 at the time of the track correspond to the magnitude of the signal read by the on-track head 15R overlapping the write spiral servo pattern SSP 5. In the on-track read signal intensities RS41, RS42, RS51, and RS52, the vertical lines correspond to the read signal intensities at which the sync marks are read.

In the example shown in fig. 16, the MPU60 writes the overlapped write erase pattern SSP4 by overwriting the erase pattern EP4 on the center portion of the width of the overlapped write spiral servo pattern SSP4 obtained by overlapping the spiral servo patterns SSP41 to SSP46 in the forward direction on the disk 10. The MPU60 writes the overlapped-writing and erasing spiral pattern SSP5 by overwriting the erasing pattern EP5 on the central portion of the width of the overlapped-writing and erasing spiral pattern SSP5 obtained by overlapping the spiral servo patterns SSP51 to SSP56 in the clockwise direction on the disk 10 with an interval in the time direction from the overlapped-writing and erasing spiral pattern SSP4.

In the example shown in fig. 16, the MPU60 reads the write-overlap erase spiral patterns SSP4 and SSP5 by bringing the head 15R on track according to the on-track path ORR2, and obtains on-track read signal intensities RS41, RS42, RS51, and RS52.

Fig. 17 is a schematic diagram showing an example of a write processing method of overlapping write/erase spiral patterns according to embodiment 2. Fig. 17 shows the overlapping write erase spiral patterns SSP4 (SSP) and SSP5 (SSP) shown in fig. 16. Fig. 17 shows the seek path SRR2 of the head 15R at the seek time with respect to the overlap write erase spiral patterns SSP (SSP 4 and SSP 5). The read signal strengths RS43, RS44, RS53, and RS54 at the time of seek are shown in fig. 17. The read signal intensities RS43 and RS44 at the time of seek correspond to the magnitudes of signals read by the overlapped write erase spiral pattern SSP4 by the reading head 15R that is seeking. The read signal intensities RS53 and RS54 at the time of seek correspond to the magnitudes of signals read by the head 15R that is seeking to the superimposed write-erase spiral pattern SSP5.

In the example shown in fig. 17, the MPU60 seeks the head 15R according to the seek path SRR2 to read the overlapped write/erase spiral patterns SSP4 and SSP5, and obtains the seek-time read signal intensities RS43, RS44, RS53, and RS54.

Fig. 18 is a schematic diagram showing an example of a calculation method of the erase pattern center position of the overlapped write erase spiral pattern SSP4 according to embodiment 2. Fig. 18 shows the overlap write erase spiral pattern SSP4, the on-track path ORR2, and the on-track read signal strengths RS41 and RS42 of the overlap write erase spiral pattern SSP4 shown in fig. 16. Fig. 18 shows an erase spiral demodulation MAG value corresponding to the on-track read signal strengths RS41 and RS42 of the superimposed write erase spiral pattern SSP4, an erase spiral difference value between the Maximum (MAX) erase spiral demodulation MAG value and the erase demodulation MAG value among the erase spiral demodulation MAG values, and a difference integrated value (hereinafter, also referred to as an on-track difference integrated value or a difference integrated value) corresponding to the erase spiral difference value. The horizontal axis of the erase spiral demodulation MAG value, erase spiral delta value, and delta accumulation value is time.

In the example shown in fig. 18, the MPU60 acquires each erase spiral demodulation MAG value corresponding to each timing at which a Sync mark (Sync) is detected, based on the on-track read signal strengths RS41 and RS42 of the overlap write erase spiral pattern SSP 4. The MPU60 calculates the maximum erase spiral demodulation MAG value of the erase spiral demodulation MAG values of the overlay write erase spiral pattern SSP4 and the erase spiral difference values of the erase demodulation MAG values. The MPU60 calculates a difference integrated value obtained by integrating these individual erase spiral difference values, and calculates a position corresponding to the timing of half (0.5) of the difference integrated value as the erase pattern center position of the overlap-write erase spiral pattern SSP 4. The MPU60 may record the calculated center position of the erase pattern of the overlapped writing erase spiral pattern SSP4 in a predetermined recording area, for example, the disk 10, the volatile memory 70, the nonvolatile memory 80, or the buffer memory 90.

The MPU60 writes a predetermined spiral servo pattern (normal spiral servo pattern) SSP (B1201) on the disk 10, and writes another spiral servo pattern (normal spiral servo pattern) SSP by overlapping the spiral servo pattern (normal spiral servo pattern) SSP with the predetermined offset in the forward direction (B1202). The MPU60 determines whether or not to write a spiral servo pattern (normal spiral servo pattern) SSP in an overlapping manner (B1203). If it is determined that the spiral servo pattern SSP (normal spiral servo pattern) is to be superimposed (yes in B1203), the MPU60 proceeds to the process in B1202.

When it is determined that the spiral servo patterns SSP (normal spiral servo patterns) are not to be superimposed (no in B1203), the MPU60 overwrites the erase pattern on the center of the width of the superimposed spiral servo patterns SSP obtained by superimposed writing of the plurality of spiral servo patterns SSP (B1901), and ends the processing.

The MPU60 reads a spiral servo pattern, for example, an overlapped-writing erase spiral pattern SSP (B2001), and acquires each demodulated MAG value every time a synchronizing mark of a read signal of the overlapped-writing erase spiral pattern SSP is detected (B2002). MPU60 calculates the maximum erase spiral demodulation MAG value of each demodulation MAG value of the overlay write erase spiral pattern SSP and each erase spiral difference value of each erase demodulation MAG value (B2003). The MPU60 calculates a difference integrated value obtained by integrating the respective erase spiral difference values (B2004), calculates a position corresponding to a timing corresponding to half of the difference integrated value as an erase pattern center position (B2005), and ends the process.

According to embodiment 2, the magnetic disk device 1 writes the overlapping write spiral pattern SSP by overwriting the erase pattern on the center portion of the width of the overlapping write spiral servo pattern SSP. The magnetic disk device 1 reads the superimposed write/erase spiral pattern SSP, and acquires each demodulation MAG value every time the sync mark of the read signal of the superimposed write/erase spiral pattern SSP is detected. The magnetic disk device 1 calculates the maximum erase spiral demodulation MAG value among the demodulation MAG values of the superimposed write erase spiral pattern SSP and the erase spiral difference value of each erase demodulation MAG value. The magnetic disk device 1 calculates a difference integrated value obtained by integrating the respective erase spiral difference values, and calculates a position corresponding to a timing corresponding to half of the difference integrated value as an erase pattern center position. Even if the width of the spiral servo pattern varies when the overlapping writing accuracy is not sufficiently obtained, the disk device 1 overlaps and writes a plurality of spiral servo patterns SSP without a gap, and overwrites the erase pattern. Therefore, even if the head 15 having a narrow writing width is written in the magnetic disk device 1, defects in the SSW process and the like can be reduced. Therefore, the magnetic disk apparatus 1 can improve reliability.

Several embodiments are described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. These embodiments and/or modifications thereof are included in the scope and/or gist of the invention, and are included in the invention described in the claims and the scope equivalent thereto.

Claims

1. A magnetic disk device is provided with:

a disk;

a head that writes data to the disk and reads data from the disk; and

and a controller for overlapping and writing a 2 nd spiral servo pattern different from the 1 st spiral servo pattern with a shift in a radial direction of the disk.

2. The magnetic disk apparatus according to claim 1,

the controller performs positioning control based on a MAG value associated with a read signal that reads an overlapping written spiral servo pattern obtained by overlapping writing the 2 nd spiral servo pattern with the 1 st spiral servo pattern in the radial direction.

3. The magnetic disk apparatus according to claim 2,

the controller calculates a position corresponding to a timing of half of an integrated value obtained by integrating the MAG value as a center position of a width of the overlapping write spiral servo pattern.

4. A magnetic disk apparatus according to claim 3,

the controller calculates a position error based on the center position.

5. The magnetic disk apparatus according to claim 1,

the controller writes an erase pattern in a central portion of a width of the overlapped write spiral servo pattern obtained by overlapping the 1 st spiral servo pattern with the 2 nd spiral servo pattern in the radial direction.

6. The magnetic disk apparatus according to claim 5,

the frequency of the erase pattern is greater than the frequency of the 1 st spiral servo pattern and the 2 nd spiral servo pattern.

7. The magnetic disk device according to claim 5 or 6,

the controller writes the erase pattern only once to the central portion.

8. The magnetic disk device according to claim 5 or 6,

the controller performs positioning control based on a MAG value associated with a read signal that reads the overlapping written-erase spiral pattern obtained by writing the erase pattern in a central portion of the width of the overlapping written-spiral servo pattern.

9. The magnetic disk apparatus according to claim 8,

the controller calculates a difference value between a maximum value of the MAG values corresponding to the overlapped writing erase spiral pattern not including the erase pattern and the MAG values corresponding to the overlapped writing erase spiral pattern including the erase pattern, and calculates a position corresponding to a timing of half of an integrated value obtained by integrating the difference value as a center position of a width of the overlapped writing erase spiral pattern.

10. The magnetic disk apparatus according to claim 9,

The controller calculates a position error based on the center position.

11. A servo pattern writing method applied to a magnetic disk apparatus including a disk and a head that writes data to the disk and reads data from the disk, the servo pattern writing method comprising:

a2 nd spiral servo pattern different from the 1 st spiral servo pattern is written so as to overlap with the 1 st spiral servo pattern with a shift in the radial direction of the disk.